Shader "LearnShader/GaoSiMoHu"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _Sigma ("Sigma",Range(0.001,0.1)) = 0.001
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // make fog work
            #pragma multi_compile_fog

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                UNITY_FOG_COORDS(1)
                float4 vertex : SV_POSITION;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;
            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _MainTex);
                UNITY_TRANSFER_FOG(o,o.vertex);
                return o;
            }

            float _Sigma;
            fixed4 frag (v2f i) : SV_Target
            {
                float2 tempUV = i.uv;

                fixed4 col_0 = tex2D(_MainTex, tempUV);
                fixed4 col_1 = tex2D(_MainTex, tempUV+float2(_Sigma,_Sigma));
                fixed4 col_2 = tex2D(_MainTex, tempUV+float2(_Sigma,-_Sigma));
                fixed4 col_3 = tex2D(_MainTex, tempUV+float2(-_Sigma,_Sigma));
                fixed4 col_4 = tex2D(_MainTex, tempUV+float2(-_Sigma,-_Sigma));
                fixed4 col_5 = tex2D(_MainTex, tempUV+float2(0,_Sigma));
                fixed4 col_6 = tex2D(_MainTex, tempUV+float2(0,-_Sigma));
                fixed4 col_7 = tex2D(_MainTex, tempUV+float2(-_Sigma,0));
                fixed4 col_8 = tex2D(_MainTex, tempUV+float2(_Sigma,0));

                fixed4 col = (col_0+col_1+col_2+col_3+col_4+col_5+col_6+col_7+col_8)/9;
                // apply fog
                UNITY_APPLY_FOG(i.fogCoord, col);
                return col;
            }
            ENDCG
        }
    }
}
